A rare-earth-based (RE123-based) oxide superconducting wire has a structure in which an oxide superconducting layer and a metal stabilizing layer are laminated on a tape-shaped metal substrate with an intermediate layer interposed therebetween. Therefore, in order to reduce AC loss, a multi-filament structure needs to be formed by subdividing the oxide superconducting layer.
Hitherto, in order to form a multi-filament structure from a rare-earth-based oxide superconducting wire, a masking tape attached to the surface of the wire is irradiated with a laser having a weak output to partially remove the masking tape, and through the remaining masking tape, chemical etching is performed on a metal stabilizing layer made of Ag and an oxide superconducting layer in two stages. Through the chemical etching, a plurality of dividing grooves are formed to divide the stabilizing layer and the oxide superconducting layer into an arbitrary number of sections, thereby forming a multi-filament structure having a plurality of superconducting filaments.
However, in the method of forming the dividing grooves through etching, there is a limit to a reduction in the groove width, and an over-etched region is likely to be generated in the edge portion of the superconducting filament. For this reason, there are problems of a reduction in critical current and peeling of the superconducting filament.
Specifically, the dividing grooves formed in the oxide superconducting layer become wider than the grooves formed in the metal stabilizing layer in the chemical etching process, and thus it is extremely difficult to allow an effective groove width formed in the oxide superconducting layer to be equal to or less than 100 μm.
In addition, the method of manufacturing the oxide superconducting wire having the multi-filament structure in combination with the masking tape, laser irradiation, and chemical etching described above is limited to a case where the metal stabilizing layer is made of Ag. For example, in a case of using a Cu stabilizing layer, which is most commonly used in an oxide superconducting wire, an etchant which is effective for Cu without causing corrosion of the oxide superconducting wire is not developed in the current situation. Therefore, dividing grooves may not be formed by partially removing Cu through etching.
In addition, as a technique for forming an oxide superconductor having a multi-filament structure by dividing an oxide superconducting layer using laser irradiation, as described in Patent Document 1 below, a technique for dividing an oxide superconducting layer into a plurality of sections in the width direction of the oxide superconducting layer by focusing laser light on the oxide superconducting layer along the longitudinal direction thereof is known.
According to the technique described in Patent Document 1, it is described that while the laser light is focused on the oxide superconducting layer, a molten material in the dividing grooves is blown off by purge gas, such that a multi-filament wire having a structure in which the oxide superconducting layer is divided can be manufactured.